Amendment to Settlement Agreement and Asset Sale Agreement

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Exhibit 10.10b

AMPHASTAR PHARMACEUTICALS, INC.

March 27, 2006

Organon USA Inc.
56 Livingston Ave.
Roseland, NJ, 07068
Attention: Huib Costermans, Chief Financial Officer

Re:     Amendment to Settlement Agreement and Asset Sale Agreement

        This is to confirm our understanding concerning the $6 million final payment (the "Payment") owed in February 2006 by Amphastar to Organon under the Settlement Agreement dated December 20, 2004, and the Asset Sale Agreement entered into by the parties in 2003, as amended, pertaining to the sale of the U.S. product rights to Cortrosyn.

        In consideration of a loan fee of $75,000 (the "Fee") and the mutual promises contained herein, Amphastar agrees to make the Payment to Organon as follows:

1.

$1 million to be received by Organon no later than March 31, 2006;

2.

$1 million to be received by Organon no later than April 30, 2006;

3.

$1 million to be received by Organon no later than May 31, 2006; and

4.

$3 million to be received by Organon no